Today, the Supreme Court will hear arguments on a challenge to California's Proposition 8, a voter-passed initiative that defines marriage as only between a man and a woman.

On Wednesday, the justices will hear a challenge to the Defense of Marriage Act, a 1996 federal law that defines marriage as between a man and a woman. DOMA, as it is known, allows states to refuse to recognize same-sex marriages performed in other states.

The two cases "have much in common," said Vik Amar, a law professor at the University of California at Davis who hasn't been involved in the cases. "Both cases ask the basic question: How skeptical should courts be under equal protection principles about laws that discriminate against gays and lesbians?"

Experts say the two cases could lead to a wide array of decisions. Let's take a look.

The DOMA case: United States vs. Windsor.

Edith "Edie" Windsor lived with Thea Spyer for 44 years, and the New York couple was married in Canada in 2007. After Spyer's death in 2009, Windsor had to pay taxes on her spouse's estate rather than inheriting it outright. Windsor sued the government, arguing that DOMA was unconstitutional because it violated the Constitution's equal protection clause.

In an unusual but not unprecedented move, the U.S. Department of Justice under President Barack Obama has declined to defend the law. So DOMA's case is being taken up by lawyers hired by a panel of the Republican-controlled House of Representatives.

The Prop 8 case: Hollingsworth vs. Perry.

In 2009, two same-sex couples — Kristin Perry and Sandra Stier, and Paul Katami and Jeffrey Zarrillo — were denied marriage licenses after passage of Proposition 8 in November 2008. The two couples sued, claiming that the Constitution's equal protection clause prohibits California from defining marriage as the union of a man and a woman.

Democratic Gov. Jerry Brown has also declined to defend the law. Instead, a group that supported the original ballot initiative is defending the decision.

Some key legal issues

• Is there a fundamental right to marry? Those who oppose marriage for same-sex couples argue that society has an interest in drawing distinctions because married couples can procreate. Supporters reject that view. "I think a critical line of questions, perhaps from Justice Anthony Kennedy, about the purpose of marriage, will shed a great deal of light on the court's thinking about the cases," said Chapman University law professor John Eastman, who has filed friend-of-the-court briefs in support of DOMA and Prop 8.

• What is the proper balance in powers between the federal government and the states? Historically, the idea that the federal government has overstepped its mandate in relation to state powers has been attractive to conservative justices, so the possibility of that rationale being used in this case in service of a liberal policy goal is considered noteworthy.

• What level of "scrutiny" should be provided for equal protection? Supporters of marriage equality argue that laws discriminating against lesbians and gay men should be subjected to "heightened scrutiny," meaning the government must put forth a compelling and specific need for the discrimination. Heightened scrutiny already exists for racial and gender discrimination, but applying heightened scrutiny to sexual orientation would be a first, said Dale Carpenter, a University of Minnesota law professor who has filed a brief in support of overturning DOMA.

Some ruling options

Uphold both Prop 8 and DOMA. Upholding both laws would be a serious strike against same-sex marriage. The status quo would stand — no same-sex marriage in California, and no federal recognition of same-sex marriage.

Punt, citing questions of "standing." The justices could decide that the backers of Prop 8 (or possibly DOMA) aren't the right parties to defend the law — a route the Supreme Court took a few times while grappling with the legality of interracial marriage before deciding the issue in 1967 in Loving vs. Virginia, said Kermit Roosevelt, a University of Pennsylvania law professor who has filed a brief arguing that DOMA has a negative impact on child welfare. This sort of ruling would amount to kicking the can down the road.

A mixed decision. "It's possible for the court to strike down DOMA without even considering the question of whether there is a constitutional right to same-sex marriage, because defining marriage is beyond the power of the federal government, regardless of whether there is any individual right involved," said Ilya Somin, a George Mason University law professor who signed a brief making that argument.

Support same-sex marriage on very limited grounds. The court could rule that any state that had once allowed same-sex marriage can't take it away. This would make same-sex marriage legal in California, but the ruling wouldn't be applicable in other cases.

Support same-sex marriage in a more middle-of-the-road fashion. The court could rule that if states have civil unions that are legally identical to marriage, then they cannot deny the label "marriage" to same-sex couples. This would affect eight states that currently have spousal rights short of marriage.

Support same-sex marriage everywhere all at once. The justices could in one fell swoop announce that there is a right to same-sex marriage in all 50 states. This would be a huge decision that essentially settles the debate.

Meanwhile, any decision that struck down DOMA would have significant consequences very quickly, said Hayley Gorenberg, deputy legal director of Lambda Legal, a legal organization for lesbian, gay, bisexual and transgender rights. Such a decision "would allow married couples a host of federal benefits and responsibilities," she said.

But any ruling short of a 50-state solution "is likely to be a placeholder until other cases force the court to say more in the next handful of years," Amar said.

There is a reason why the air in Tampa Bay is filled with playoff talk. If Thursday night's 12-8 Bucs preseason win over the Jaguars is any indication, it's also going to be filled with footballs thrown by quarterback Jameis Winston.